\documentclass[12pt, twoside]{article}
\usepackage{tikz}

\begin{document}
\begin{figure}
    \centering
    \begin{tikzpicture}[
dot/.style = {circle,fill=black,inner sep=1pt, node contents={}},
every node/.append style = {text depth=0.2ex}
                        ]
\draw[very thick] (0,0) node (1)   [dot,label=$1$]  -- (1,0);
\draw[very thick] (1,0) node (2)   [dot,label=$2$]  -- (2,0);
\draw[very thick] (2,0) -- (4,0);
\draw[very thick] (4,0) node (i-1) [dot,label=$i-1$] -- (5,0);
\draw[very thick] (5,0) node (i)   [dot,label=$i$]   -- (6,0);
\draw[very thick] (6,0) node (i+1) [dot,label=$i+1$] -- (7,0);
\draw[very thick] (7,0) -- (9,0);
\draw[dotted,very thick] (9,0)  node (N)   [dot,label=$N$] -- 
                         (10,0) node (N+1) [dot,label=$N+1$];
    \end{tikzpicture}
    \caption{Visualization of meshing elements and intervals including the complex $N+1$ node}
    \label{fig:nodeline}
\end{figure}
\end{document}
